1. Field of the Invention
The invention relates to apparatus for the rapid thermal energy removal of superfluous projections on articles such as metal and plastic workpieces. Apparatus of this type uses a closed chamber in which the articles are placed with voids around them, combustible gases being forced into the closed chamber and ignited to obtain a rapid release of thermal energy which removes the projections, such as burrs and the like.
2. Description of the Prior Art
Rice U.S. Pat. No. 3,666,252 shows an apparatus of this type in which the upper closure of the chamber is supported by a C-frame with a plurality of lower closures supported by a turntable. After articles are placed on each lower closure, it is lifted by a toggle mechanism into engagement with the upper closure, the toggle mechanism exerting a very high force in order to seal the closures together. This machine had a number of drawbacks which it is an object of the present invention to overcome. The high force exerted by the toggle mechanism required an equivalently strong C-frame which in turn limited, as a practical matter, the size of the chamber which could be employed. The type of parts which could be placed in the chamber was also limited, since the toggle mechanism stroke was not large. The high sealing forces were apt to distort the C-frame which could cause a curved motion of the lower closure onto the upper closure, possibly resulting in the galling of important surfaces. The large hydraulic pump and electric motor required to drive the toggle mechanism also causes excessive noise and heat. Furthermore, the tremendous forces involved could cause loss of lubrication in the toggle mechanism, resulting in the tendency to remain at times in a locked position.
Machines built along the lines of the disclosure in the above-mentioned patent had other drawbacks which the present invention overcomes. The seal between the lower and upper closures was previously a gasket seal which required high pre-loading, with the resultant chamber size limitations and clamping force problems mentioned above. Cooling of the lower closures on the turntable was quite difficult to achieve. The mixing valves were of a tapered or needle type held in closed position by hydraulic cylinders and so arranged that the explosion in the chamber tended to open them, thus requiring high closing forces. The valves were also exposed to high transient heat which took place in the chamber. After ignition of the mixture, the exhaust gases were released by lowering the lower closure, a procedure which would be destructive if uncompensated seals were used. It was difficult to place high pressure charges of combustible gases in the chamber because of the large charging cylinder volumes which would be required. The gas charging cylinders in the previous apparatus were horizontally mounted, thus allowing the lubricant to occasionally run into the oxygen line and cause pre-ignitions.
Rice et al. U.S. Pat. No. 3,547,589 discloses a shuttle type pressure vessel structure for processing stock, requiring at least a pair of pressure vessel elements shuttled between stations. The present invention incorporates a different means for alternately moving workpieces into position to be processed, is constructed on different principles and has the important advantage over the patented structure of avoiding the cumbersomeness of moving an entire pressure vessel structure into and out of the working position.